Ring and cord or loop puzzles which involve the same manipulative operations as the puzzle illustrated and described herein have existed fo a substantial period of time. The principle of operation is substantially the same with respect to each of the known prior art structures and the manipulation in solving the puzzles follows the substantially same sequential procedure.
Examples of prior art puzzles of this type are disclosed in recently issued U.S. Pat. Nos. 3,881,732; 3,706,458; and 3,698,719. Each of these patented puzzles includes a base, a plurality of rings that are each connected with the base and are interrelated with a next adjacent ring. A rigid loop is provided for interlockingly coupling with all of the rings and is relatively manipulated to be disengaged from all of the rings. It will be noted that in U.S. Pat. 3,881,732, the base is not a unitary member but comprises enlarged discs connected with each ring. However, in each patented puzzle, the rings are connected to the base by means of separate post elements that are relatively movable to the other posts to permit operative manipulation of the rigid loop. This multiplicity of relatively movable elements renders these puzzles particularly difficult to work and substantially complicates the basic manipulative function to effect a solution of the puzzle.
Prior art puzzles of this type having rigid base, post and ring structures with a flexible cord loop are also known. Examples of this type are disclosed in U.S. Pat. Nos. 1,091,709and 2,324,566. These puzzles comprise structures that are difficult to fabricate and are not readily adapted to mass production techniques. Additionally, these puzzles are only workable with a completely flexible cord which can result in difficulty in maintaining the cord in proper relationship to the post and rings during working of the puzzle and these puzzles do not have the advantage of articulated rings.